Parting locking devices are mainly used in three-plate type injection molding machines.
A three-plate type injection molding machine includes a fixed mold and a movable mold defining, between the fixed and movable molds, a cavity for molding resin into a predetermined shape, and a stripper plate configured to be brought into contact with and separated from the movable mold. Two parting locking devices are used in a three-plate type injection molding machine to separate, when opening the cavities, the stripper plate from the movable mold before separating the movable mold from the fixed mold.
The distal end of a spool bush of this injection molding machine is inserted into the stripper plate so that molten resin supplied through the inserted spool bush is guided to a gate provided in the movable mold, and is injected into the cavity.
Thereafter, the stripper plate is separated from the movable mold before the movable mold is separated from the fixed mold so that a runner portion formed between the stripper plate and the movable mold is separated from the product made of the resin injected into the cavity.
Thereafter, the movable mold is separated from the fixed mold, and the now-hardened product in the cavity is taken out of the fixed mold.
By moving/separating the stripper plate from the movable mold before separating the movable mold from the fixed mold, it is possible to prevent the deformation of the product.
The above method requires that the movable mold be coupled to the fixed mold (the separation of the parting surfaces be prevented) until the stripper plate is moved to a predetermined position, and the runner portion is separated from the product. In order to satisfy this requirement, parting locking devices are used.
Conventional parting locking devices are disclosed or illustrated, for example, in Japanese Patent (JP) 3761690 and Japanese Unexamined Patent Application Publication (JP) 2008-119953, and FIG. 10 of the present application.
The parting locking device of FIG. 10 is disclosed as prior art in JP 3761690, and includes a locking bar 51 mounted to a stripper plate 35.
The locking bar 51 is inserted between a base holder 55 and an engagement claw 53 pivotable about a support pin 52, thereby keeping the engagement claw 53 in engagement with a locking claw 54
When the locking bar 51 is pulled out of the base holder 55, the engagement claw 53 is disengaged from the locking claw 54, and a locking member 56 is uncoupled from the base holder 55, so that a movable mold 34 can be separated from a fixed mold 32.
The parting locking device of the invention of JP 3761690 differs from this prior art in that the locking member includes an insertion portion capable of being inserted into and pulled out of the base holder.
Engagement elements retained on the respective sides of the insertion portion are pushed toward the outside of the insertion portion by the locking bar such that the portions of the engagement elements protruding beyond the insertion portion are engaged in engagement recesses provided in the base holder.
This engagement state is maintained by the locking bar being inserted in a hole of the insertion portion. As a result thereof, it is possible to maintain the coupled state of the base holder and the locking member, which are mounted to the fixed mold and the movable mold, respectively, and thus to prevent the movable mold from being separated from the fixed mold.